My Civic started acting up about a month ago.

My civic started acting up about a month ago, it started to over heat on me and I work in a mechanic shop so when I got to work I checked everything out. Had to get a new radiator. But I couldnt get a cap cuz of money issues, so the day I was going to get a cap my car cut out on me. I noticed oil was mixing with my antifreeze. I changed my head gasket, radiator, radiator cap and thermostat. I put it all back together and flushed my rad for 3 hours, seemed it was getting back how it was. I drove it for a min and checked nothing changed, now I also have a oil leak but it only leaks when I run the car. Please help